1. Technical Field
The invention relates to a hinged base for a shoring strut for use in construction and steel structural work.
It particularly relates to a hinged base for perpendicular and inclined metal shoring struts, comprising a ball joint with a wide solid angle rotation range. The components of such hinges are a support element in contact against a structure to be shored and a head removably (so that the ball joint elements can be separated) housed in a seat afforded in the base element and connectable to a shore.
2. Prior Art
Ball hinge joints exist in the prior art, though none of them are directly applicable to shores. In these prior art solutions, the removability of the head from the ball seat is achieved in various ways. For example, in patent DE 37 30 678 A1, a type of ball joint hinge is used in which the support element exhibits a substantially cylindrical seat bordered by removable pivots. Patent DE 18 90 440 exhibits a ball-joint for rod linkages, comprising two side-by-side rigid semihousings together forming a spherical seat, which semihousings are held removably together by means of a sleeve-coupling. DE 40 41 939 exhibits a ball seat realized internally of a support element and is made with a plastically deformable metal shell; a plastic gasket being interposed between the support element and the ball head. DE 31 32 824 discloses a ball seat made by means of a pair of coaxial sleeves and a holed plate.
While none of the above-mentioned ball-joints are truly applicable in the construction industry for forming a shoring base, Italian patent for Utility Model no. TA91U000003, entitled "Components for Realizing Wide-angle Shorings for Building Structures", by the same applicant, partially satisfies said requirement. The components of the above patent comprise: a shore exhibiting at one end a coupling zone; a terminal element composed of a spherical portion, a cylindrical portion and a coaxial tang which can be jointed in the corresponding end of the shore; a straight prismatic triangular support element, basically semi-cubically shaped, provided with a hemispherical cavity in its diagonal face which functions as a ball-joint seat for the above-mentioned terminal element.
In the above patent, the terminal element and the support element together constitute the base of the shore. The terminal element is inclinable through a wide angle so that the resulting shoring strut can be perpendicular or inclined, while the support base exhibits a multiplicity of trihedrons, each of which presents a face acting as a rest surface for the shoring zone (the contact surface) and two more faces, perpendicular to the first face and acting as bucks to the contact surface. The bucking surfaces are in contact with the dihedron or trihedron constituting the structure to be shored, for example a floor and one or two walls, or with the surfaces of other like support elements meeting in a complex shoring strut arrangement.
The above-described patent exhibits some drawbacks, however, not so much from the functional point of view as from that of the difficulties encountered in the installation of the bases of the shore, especially when a base is applied to a ceiling or in general to a projecting structure. These difficulties are due to the instability of the relationship between the terminal element and the support element due to the fact that the portion of head of the former is simply housed and not constrained solidly in the seat of the latter. Further, it is impossible to achieve a blocking of single support elements which will be associated together in a same complex shoring joint arrangement, as mentioned above.
Other drawbacks encountered in the above-mentioned patent are connected with the functionability of the support base, such as its inability to deal with tangential forces which might build up on the active surfaces (that is, the contact and bucking surfaces) of the shorings.